Unable to set permissions for an external content type (Permissions list is empty)

I created a BDC model that is connected to a WSDL web service:

<LobSystem Name="TestWSModel" Type="Wcf">
      <Properties>
        <Property Name="WcfMexDiscoMode" Type="System.String">Disco</Property>
        <Property Name="WcfMexDocumentUrl" Type="System.String">http://localhost:8000/WebService.asmx?wsdl</Property>
        <Property Name="WcfProxyNamespace" Type="System.String">BCS.WCFProxy</Property>
        <Property Name="WildcardCharacter" Type="System.String">*</Property>
      </Properties>
      <LobSystemInstances>
        <LobSystemInstance Name="TestWSModel">
          <Properties>
            <Property Name="WcfEndpointAddress" Type="System.String">http://localhost:8000/WebService.asmx</Property>
          </Properties>
        </LobSystemInstance>
      </LobSystemInstances>
      ...
</LobSystem>

External content type is created succeddfully, but I am unable to set permissions, 'cause persmissions list is empty:

But when I create the model using designer (in this case it has the "DotNetAssembly" type) everything works fine.

Am I missing something?